Container closures with breakable openings



J. A. GEIGER CONTAINER CLOSURES WITH BREAKABLE OPENINGS Filed Aug. 24;1964 4 Sheets-Sheet l INVENTOR J 7M Jan. 9, 1968 J. A. GEIGER CONTAINERCLOSURES WITH BREAKABLE OPENINGS 4 Sheets-Sheet 2 Filed Aug. 24, 1964www- Jan. 9 1968 J. A. GEIGER CONTAINER CLOSURES WITH BREAKABLE OPENINGS4 Sheets-Sheet .3

Filed Aug. 24, 1964 INVENTOR )M r y Jan. 9, 1968 I J. A. GEIGER3,362,569

CONTAINER CLOSURES WI TH BREAKABLE OPENINGS Filed Aug. 24, 1964 4Sheets-Sheet 4 INVENTOR United States Patent 3,362,569 CONTAINERCLOSURES WITH BREAKABLE OPENINGS Joseph A. Geiger, Wolfurt, Vorarlberg,Austria (3030 Platten Drive, Fairfax, Va. 22030) Filed Aug. 24, 1964,Ser. No. 391,520 11 Claims. (Cl. 220-48) The present invention relatesto container closures with easy-opening features and more particularlyto metallic container closures with prepared easy-breakable openingsections. The invention has particular merit when embodied inhermetically sealed cans for liquids, such as carbonated beverages,which are subjected to internal pressures.

Many efforts have been made in recent years to develop containers withnew and better opening features. The present developmental trend in therigid container industry is to eliminate previously required specialopening tools through the provision of scoring lines or otherappropriate local weakening in the container wall, so that a section ofit can be torn off with relatively little effort, using finger force forpulling.

Containers featuring integral tear-open devices have received widespreadacceptance as beverage cans and in particular as beer and soft drinkcans. However, the presently available designs, featuring in general anelongated tear-section with a short pull-tab, have been the subject ofserious criticism, based upon mainly the following three objections: (a)the relatively hard pull required to initiate tearing, and the resultantdanger of injury to the pulling fingers; (b) the hazard of inadvertantlycutting ones fingers or lips on the sharp edges created along theoutside of the tear-section and around the opening; and (c) the hazardof foot injuries to children on public sand beaches and play groundswhere carelessly discarded tear-sections represent a growing problem.

On the other hand it is necessary for most of these containers towithstand considerable internal pressures which may occur duringin-package pasteurization, in-package cooking, or as a result ofcarbonation. The provision of an easy-opening feature in such acontainer, therefore, calls for the inherently diflicult combination ofeasy breakability of the container wall with structural strength andleak-tightness.

In addition to the mechanical and physical features referred to above itis a primary and decisive requirement for any such container, orcontainer component, to be as inexpensive as possible to justify massproduction.

It is therefore one of the objects of this invention to provide aninexpensive one-piece metallic end closure for a pressure-resistantcontainer, having easily breakable wall portions defined by a line ofweakening in the closure wall.

It is another object of this invention to provide an end closure of thetype mentioned above with breakable wall portions hinged to the closurewall and hence nondetachable.

A further object of this invention is to provide an end closure of thetype mentioned where the breakable Wall portions are pivoted toward theinside of the container and no cutting edges are exposed to theexterior.

It is still a further object of this invention to provide an end closurewith easily breakable wall portions where the severance at the line ofweakening can be initiated by either the direct pressure of -a finger orthe assisting leverage of a rigid object, such as a coin, fiat door keyor other readily available object.

Various other objects and advantages of the invention will becomeapparent as it is better understood from 3,362,569 Patented Jan. 9, 1968the following description which, taken in connection with theaccompanying drawings, discloses several preferred embodiments thereof.

In accordance with the above objects, and as a feature of thisinvention, there is provided a one-piece metallic end closure for acontainer with predetermined removable wall portions on its surfacedefined by lines of weakening in the closure wall and produced bypartially shearing the wall in a die and displacing it toward theinterior of the closure, with the central part of the removable wallportions protruding to the exterior and shaped with a groove where acoin or flat key can be applied to sever the removable wall portions andpivot them toward the interior of the container.

Accordingly also, as another feature of this invention, provision ismade for a metallic end closure as outlined above, with lines ofweakening of non-uniform residual width and resistance againstseverance, in correspondance with the stress pattern of the closureunder internal pressure, and rib structures on the removable wallportions facilitating the initiation of severance under an exteriorforce, through load concentration at specific points on the line ofweakening. Ordinarily, direct thumb pressure will suffice to initiatethis severance. However, a mechanical advantage will be gained with theutilization of a coin or key as stated above. The versatility thusprovided is intended to increase the usefulness of the in vention.

The above and other features of the invention, including various noveldetails of construction and combination of parts will now be morespecifically described with reference to the accompanying drawings andpointed out in the claims. It will be understood that the particular endclosures embodying the invention are shown by way of illustration onlyand not as a limitation of the invention. The principles and features ofthis invention may be employed in varied and numerous embodimentswithout departing from the scope of the invention.

In the drawings in which like reference characters indicate like partsthroughout the several views:

FIGURE 1 is a top plan view of an end closure having two removable wallportions, one of them broken open, and embodying the invention.

FIGURE 2 is a sectional view of the end closure of FIG. 1.

FIGURE 3 is a top plan view of an end closure having a single elongatedremovale wall portion as a modified embodiment of the invention.

FIGURE 4 is a sectional view of the end closure of FIG. 3.

FIGURE 5 is an enlarged fragment of FIG. 1.

FIGURE 6 is a fragmentary sectional view taken along lines VI-VI of FIG.5.

FIGURE 7 is a fragmentary sectional view taken along lines VIIVII ofFIG. 5.

FIGURE 8 is a fragmentary sectional view similar to FIG. 7, illustratinga modified embodiment of the invention.

FIGURES 9 and 10 are fragmentary sectional views similar to FIGS. 7 and8, illustrating two further embodiments of the invention.

FIGURES 11 through 14 are greatly enlarged fragmentary cross sections ofthe end closure at different points on the line of weakening,illustrating methods of producing the latter in accordance with theinvention.

Referring to the figures enumerated above, FIGURES 1 and 2 illustrate aparticular embodiment of the invention, represented by a metallic endclosure 20 adapted to be secured to the body of a container by a doubleseam or some other convenient construction. Two removable wall portions21 and 22 are arranged diametrally opposite one another as breakableopenings and defined in their outline by lines of weakening 23 and 24.

The removable wall portion 22 is shown broken and pivoted toward theinterior of the surrounding closure wall 25, thus creating a pouringspout 26. In a similar manner removable wall portion 23 can be brokenand pivoted to create a corresponding air-admitting spout 27.

Referring now to FIGURES 5, 6 and 7, where the same embodiment isillustrated in fragmentary enlarged views, FIG. shows the removable wallportion 22 with line of weakening 24 defining a symmetric oval contourconveniently composed of four circular arc sections. Line of weakening24 is shown discontinued between points 28 and 29 situated on theinterior big arc of the contour at equal distances from point H on theintersection with the center line. The bending hinge 30 thus created isbetter illustrated in FIG. 7 at H. This view also shows a sectionthrough line of weakening 24 at the diametrally opposite point B.Closure wall 31 is partially sheared and removable wall portion 32 isdisplaced toward the interior side of closure 20 forming two narrowshear faces 33 and 34, separated by a residual wall section 35 which isintended to break when removable wall portion 32 is pushed downward withrespect to closure wall 31.

The removable wall portion 32 is provided with an exterior rib 36 and aninterior rib 37 and an approximately U-shaped groove 38 with a concavebottom wall 39. Groove 38 is flanked by an exterior face 40 and aninterior face 41, the distance between these two upright faces beingapproximately .080 inch. A coin 42 is shown engaged in groove 38 with aforce applied at its upper edge along arrow 43. The thus createdmechanical advantage permits the exertion of a leverage force toexterior rib 36 and, consequently, to line of weakening 24 at point Band over portions of the exterior big arc to both sides of point B.

The leverage achieved with a nickel, for example, would be abouteightfold, so that a finger pressure of ten pounds would produce abreaking force of about eighty pounds at line of weakening 24 adjacentto point B. As this force tends to push the exterior rib 36 toward theperiphery, and to a lesser degree also toward the interior of theclosure, it causes the residual section 35 of line of weakening 24 to besheared rather than torn. This represents a distinct advantage in termsof opening ease, as most all metals offer less resistance against shearstress than against tensile stress.

It should be self-evident that the use of a coin is mentioned by way ofillustration only and that other readily available objects, such as aflat door key or car key or a spoon handle, may be equally well or evenbetter suited for the same purpose.

Once the severence along line of weakening 24 is initiated as describedabove, it takes comparatively much less effort for its continuationalong the remaining contour of line of weakening 24. As it is pusheddownward and to the interior of closure 20, removable wall portion 22pivots around hinge 30 where the closure wall will bend rather thanbreak. This pivoting displacement stops when coin 42 comes in contactwith the narrow shear face 33 of the opening contour at point 44indicated by coin position 42a. This prevents coin 42 from beingaccidentally pushed through the spout opening.

The wall structure of removable wall portion 22, as illustrated inFIGURES 5, 6 and 7, besides permitting the aforementioned use of a coinunder a mechanical advantage, is purposely designed for an alternatemethod of opening, using the direct pressure applied with a finger andeliminating the need of an auxiliary object such as coin 42. This willbecome more apparent under the following theoretical considerations.

The end closure embodying this invention and illus trated in FIG. 2, forexample, would represent a substantially fiat end section for apressure-resistant container. Subjected to a uniform internal pressure,the end closure would yield toward the outside in the sense of bulgingto a dome-shaped position. Comparing now the stress occuring along theline of any radial vector with the stress in tangential direction, i.e.along a concentric circular line passing for example through the centerof removable wall portions 22 and 23 (FIG. 1), it becomes apparent that,while tensile stress and elongation occurs along both lines, they willbe far greater along the radial vector line. This explains thecomparative flexibility of flat end sections where it takes considerablebulging before the vectorial line is sufliciently elongated to offer thenecessary resistance. Material failure, consequently, occurs as a resultof radial stress rather than tangential stress. The radial stressincreases as the distance from the center increases.

Considering now the contour of removable wall portion 22 in FIG. 5 itwill be noticed that the residual wall section 35 along the contour ofline of weakening 24 will be subjected to non-uniform stress underinternal pressure. This stress will be at a maximum along the exteriorbig are including point B, the are being concentric with the peripheryof the end closure. It will be less at point H which is nearer theclosure center, and it will be at a minimum at the small arcs aroundpoints C and D.

In accordance with the above considerations the residual wall section 35is provided with a non-uniform width, whereby the sections of greatestweakening, or least residual width, are provided along the small arcsincluding points C and D. Two diflerent methods of creating thisnon-unform width are disclosed further below in this specification. Theactual residual width that should be chosen varies with the material andalloy of the end closure, with the dimensions chosen for the removablewall portions, their distance from the closure center, and particularly,with the requirements of pressure-resistance for the container. Theprecise dimensions are best determined by a series of routineexperiments and pressure tests. For most aluminum alloys the width ofresidual wall section 35 should preferably be about .002 inch aroundpoints C and D, and .004 inch around points B, 28 and 29 with gradualtransitions between these points. The above would be suitable, forexample, for an aluminum end closure of a beer can of 2.6 inchesdiameter. While it is preferable to use an aluminum alloy for endclosures embodying this invention, they can also be made of tin plate,in which case higher precision tooling is required.-

Referring again to FIGURES 5, 6 and 7, it can be seen that the ribstructure impressed upon wall 32 of removable wall portion 22 gives itrelative stiffness in the longitudinal direction of ribs 36 and 37, i.e.in the axis containing points C and D (FIG. 6), while giving it relativeflexibility in the transverse axis containing points B and H (FIG. 7).Accordingly, a downward force applied to the center of removable wallportion 22 will be transmitted mainly to the small arc portionscontaining points C and D, resulting in a concentration of load at andnear these points.

In a similar way, the non-removable wall portion 31 of end closure 20 isprovided with ribs 45 and 46 giving it additional stiffness in the areassurrounding points C and D. Closure wall 31 will therefore offer itsgreatest resistance against downward deflection near points C and D ofthe line of weakening 24. The combination of load concentration at andnear points C and D under a downward force as described, together withthe provision for maximum bending resistance of the wall outside pointsC and D, and a minimum residual width on the line of weakening at andnear the same points, results in a pronounced local load concentrationand a comparatively easy initiation of severance on either point C or D,depending on whether this downward force is closer to the, one or theother.

In FIGURE 8 this alternate method of opening is illus trated by a thumb53 exerting downward pressur p n removable wall portion 54 in thedirection of arrow 55. This embodiment of the invention is similar tothe one just described in detail. FIG. 8 also shows a metallic endclosure 50, a removable wall portion 51, a line of weakening 52 definingthe removable wall portion, and in addition to the features of theearlier described embodiment, an inwardly slanting rim portion 56impressed upon closure wall 57 adjacent and surrounding line ofweakening 52. Thus the opening created by breaking and pivotingremovable Wall portion 51 around hinge 58 has a recessed and protectededge 59. In addition, edge 59 of this design is blunt, i.e. the angledefined by rim portion 56 and the narrow exterior shear face 60 will begreater than ninety degrees.

FIGURES 3 and 4 illustrate an alternate embodiment of the inventioncomprising a metallic end closure 65 with the same peripheral design asthe embodiment of FIGS. 1 and 2. A single elongated removable wallportion 66 defined by a line of weakening 67 is provided to produce acombined pouring and air-admitting spout, when broken along line ofweakening 67 and pivoted inwardly as indicated by position 66a.Removable wall portion 66 comprises a generally triangular portion 68near the periphery of the closure and a narrow radial section 69continuing inwardly toward and preferably beyond the center of theclosure. At its inner end where the line of weakening 67 isdiscontinued, removable wall portion 66 terminates in a hinge '70. Thewall of removable wall portion 66 is provided with a rib structuresimilar to the one of the earlier-mentioned designs, an exterior rib 71,a groove 72 and an interior rib 73. A slight radial rib 74 is providedto apply additional pivoting force to the severed removable wall portion66a. The closure area outside the removable wall portion is reinforcedby an annular rib profile 75. The two different ways of initiatingseverance, the characteristics of the line of weakening and the otherfeatures described on earlier embodiments are or can be incorporated inthis design in the same or a similar manner.

In FIGURES 9 and still two other embodiments of the invention areillustrated. The two types are basically similar, as can readily be seenfrom the drawing. End closure 80 of FIG. 9 comprises a removable wallportion 81 with a line of weakening 82 of the previously disclosed type,a hinge 83, and in its profile, a hump-like protrusion 84-. An inwardlyextending bead 85 on the peripheral chuck wall 86 serves as a fulcrumfor coin 87 which, as mentioned earlier, can be substituted by variousequivalent or better objects. Finger pressure on coin 87 along arrow 88will result in a leverage downward force to protrusion 84 of removablewall portion 81, thereby initiating severance at the line of weakening82.

The embodiment of FIGURE 10 comprises a similar end closure 90 with aremovable wall section 91, a line of weakening 92, a hinge 93, and asimilar hump-like protrusion 94. Vertical wall 95 of removable wallsection 91, being arranged at a close distance from chuck wall 96, nobead of the kind shown in FIG. 9 is required for the creation ofmechanical advantage with coin 97. However, the direction of arrow 98implies that a slightly greater effort will be required in this case, asa certain vertical force component is required to keep com 97 engagedagainst chuck wall 96; this component contributes little to theleverage. A slanted rim portion 99, similar to the one shown in FIG. 8,serves as a protective feature and, in addition, avoids undesirablecontact between the seaming chuck (not shown) and line of weakening 92.It will be noticed that the embodiments of FIGS. 9 and 10 do not offerthe advantage of shearing action at the initiation of severance, as isthe case with the groove-type removable wall portion of earlierembodiments (compare FIG. 7). The removable wall portions of FIGS. 9 and10 could also be broken by direct finger pressure but they will requirecomparatively more effort,

6 in view of the less favorable wall profile with respect to loadconcentration.

In FIGURES 11 through 14 details indicating Ways of producing a line ofweakening and, in particular, two alternate methods of providing anon-uniform residual width along the line of weakening are illustrated.

FIGURE 11 shows the cross section of a line of weakening with a smallresidual width w which would be found at points C and D of FIGS. 5 and6, for example. Closure wall is supported by a die tool 111 while acorresponding punch tool 112 is partially shearing and displacing wall113 in a guided downward movement. The amount of shearing displacement(ta) is precisely determined and limited by stop 114 which is fixed withrespect to die tool 111 and opposes punch 112. The respective cuttingedges 115 and 116 of the tools leave a residual width w between wallportions 110 and 113. Width w is the geometric sum of the axialclearance a between tool faces 117 and 118 and the radial clearance ralong the contour of their edges 115 and 116.

FIGURE 12 shows the cross section of a line of weakening with a largeresidual width W which would be found at point B of FIGS. 5 and 7, forexample. The general arrangement is the same as in FIG. 11. However, theradial clearance between die 111 and punch 112. has been increased to Rby providing the tool with a noniclentical contour. The axial clearancea is uniform on all parts of the contour. This method of providing anonuniform line of weakening, while expensive in initial tooling costs,allows for ready re-sharpening of the tools by grinding their respectivefaces 117 and/ or 118.

FIGURE 13 shows the cross section of a line of weakening with a largeresidual width W approximately equal to the one of FIG. 12 but orienteddifferently. Again the general arrangement is the same as in FIGS. 11and 12. In this case, however, the radial clearance r is uniform on allparts of the contour, while the axial clearance between faces 117 and118 is increased to A by providing the tools with non-parallel faces 117and 118. This is achieved by locally re-grinding face 117 of the die toreduce the step (t-a) to (t-A). This alternate method of providing anon-uniform line of weakening, while less expensive in initial toolingcosts, makes re-grinding of face 117 more difficult.

In comparison with regard to the requirements of container resistanceand ease of opening, the method of radial clearance variation (FIGS. 11and 12) is preferable over the method of axial clearance variation(FIGS. 11 and 13) for these two reasons: (a) the greater overlaprepresented by R ensures better leak-tightness and safety, even under acertain limited amount of closure deformation; (b) the comparativelylesser resistance against initial severance under shearing stress, aswould occur on the groove-type removable wall portion when opened with acoin.

FIGURE 14, finally, shows the cross section of the discontinuation onthe line of weakening, adapted as a bending hinge, such as hinge 30 withpoint H of FIGS. 5 and 7, for example. The general arrangement of thetools is again the same. However, die 111 and punch 112 have their edgesground off to respective bevels 119 and 120, thereby forming a step 121in the closure wall without thereby shearing and weakening the crosssection.

It will be appreciated that the dimension of the axial clearance a maybe reduced to zero, or even be chosen to be slightly negative, so thatpunch face 118 reaches a position below die face 117. A negativedimension for a may be indicated for end closures of relativelyresilient material. 0n container end closures of average aluminum alioythe radial clearance variation method, with clearance r varying between.002 inch and .004 inch and with clearance a uniform at .0005 inch issuggested.

In the foregoing the invention has been described in reference tospecific illustrative embodiments. It will be understood, however, thatcertain variations and modifications, as well as the substitution ofequivalent elements for those shown for illustration, may be madewithout departing from the scope and spirit of the invention as definedin the appended claims. The foregoing specification and drawings areaccordingly to be regarded in an illustrative rather than in arestrictive sense.

I claim:

1. A sheet metal end closure for a pressure-resistant container with aweakening line defining the contour of a predetermined removable wallportion from a nonremovable wall portion where (a) the wall material onone side of the weakening line is displaced substantially at rightangles to the initially undisplaced surface without being severed fromthe adjacent wall material on the opposite side of the weakening line,

(b) the removable wall portion is relatively depressed toward the insideof the end closure as a result of said displacement,

(c) the edge defined by the periphery of the removable wall portionunderlaps the corresponding edge of the non-removable wall portion, andthe upper face of the removable wall portion is at or above the lowerface of the non-removable wall portion in the area of the weakeningline,

(d) the cross-sectional wall thickness in the area of the weakening linedecreases abruptly from full wall thickness to the narrowest residualconnection between the two wall portions so as to cause conditions ofstress concentration under tensional stress,

said end closure thus providing considerably differing resistanceagainst severance at the weakening line, depending on whether it issubjected to uniform internal pressure causing compression stress at theweakening line, or whether it is subjected to an opening force appliedfrom outside to the removable wall portion causing tension stressaugmented by the condition of stress concentration.

2. A sheet metal end closure as set forth in claim 1 where (e) the wallmaterial on one side of the weakening line is displaced onlysubstantially at right angles to the initially undisplaced surface,involving substantially no lateral displacement of material.

3. A sheet metal end closure as set forth in claim 1 where (f) theweakening line is discontinued and the wall material remains unweakenedover a portion of the general contour of the removable wall portion,

said end closure thus providing in addition a bending hinge for theremovable wall portion.

4. A sheet metal end closure as set forth in claim 1 where (g) the widthof the residual cross-sectional connection between the two wall portionsvaries gradually from a minimum width on one portion of the weakeningline to a maximum width on another portion,

said end closure thus providing in addition a predetermined place on thecontour of its weakening line where the said resistance againstseverance under an opening force applied from outside is the lowest.

5. A sheet metal end closure as set forth in claim 1 where (h) the widthof the residual cross-sectional connection between the two wall portionsvaries in accordance with the variation in stress over the length of theweakening line as caused by deflection of the closure wall under uniforminternal pressure,

said end closure thus providing in addition substantial uniformity overthe length of the weakening line in said resistance against severanceunder uniform internal pressure.

6. A sheet metal end closure for a pressure-resistant container with aweakening line defining the contour of a predetermined removable wallportion from a non-removable Wall portion where (a) the removable wallportion comprises in its wall structure an elongated stiffening profileextending across its center region and toward the weakening line,

(b) the major axis of elongation of said stiffening profile intersectsthe contour of the weakening line at two points,

(c) the resistance against deflection of the removable Wall portionunder an outside force applied to its center region is markedly higherin the axis of said stiffening profile as compared to the remainder ofthe removable wall portion so as to cause this force to be transmittedmainly to the points of intersection on the weakening line,

said end closure thus providing a removable wall portion which rupturesat one of two predetermined points on the weakening line when an openingforce, such as produced by thumb pressure, is applied to its center.

7. A sheet metal end closure as set forth in claim 6 Where (d) thestiffening profile comprises a groove-shaped recess which is adapted toreceive one end portion of an independent rigid member for forcibleengagement therewith and which, upon being pivoted, transmitsleverage-augmented bending load to the stiffening profile and to thepoints of intersection on the weakening line,

said end closure thus providing a removable Wall portion which, inaddition to the earlier-mentioned rupturing feature under thumbpressure, is adapted for rupturing under an alternate opening methodusing a rigid member and taking advantage of the leverage producedtherewith.

'8. A sheet metal end closure as set forth in claim 6 Where (e) theremovable wall portion is of generally arcuate contour and has itscenter region located at a distance from the closure center,

(f) the two points where the major axis of the stiffening profileintersects the contour of the weakening line are located at equaldistance from the closure center,

(g) the width of the residual cross-sectional connection between the twowall portions varies in accordance with the variation in stress over thelength of the weakening line as caused by deflection of the closure wallunder uniform internal pressure,

(h) the direction of the weakening line contour at the two points ofintersection is substantially radial with respect to the closure centerso as to coincide with portions of the weakening line where theaforementioned stress is at a minimum,

said end closure thus providing in addition to the earliermentionedpredetermined points of rupture on the weakening line for said points tooffer reduced resistance against severance without reducing the overallresistance of the end closure against uniform internal pressure.

9. A sheet metal end closure for a pressure-resistant container with aweakening line defining the contour of a predetermined removable wallportion from a non-removable wall portion where (a) the center of theremovable wall portion is located at a distance from the closure center,

(b) the contour of the weakening line is substantially oval andcomprises an exterior arc alongside the closure periphery, a smaller areon each side of said exterior arc, and an interior arc,

(c) the weakening line is discontinued and the wall material remainsunweakened over a central portion of said interior are on its contour,

(d) the wall material on one side of the weakening line is displacedsubstantially at right angles to the initially undisplaced surfacewithout being severed from the adjacent wall material on the oppositeside of the weakening line,

(e) the removable wall portion is relatively depressed toward the insideof the end closure as a result of said displacement,

(f) the edge defined by the periphery of the removable wall portionunderlaps the corresponding edge of the non-removable wall portion,

(g) the cross-sectional wall thickness in the area of the weakening linedecreases abruptly from full wall thickness to the narrowest residualconnection between the two wall portions so as to cause conditions ofstress concentration under tensional stress,

(h) the width of the residual cross-sectional connection between the twowall portions varies in accordance with the variation in stress over thelength of the weakening line as caused by deflection of the closure wallunder uniform internal pressure and consequently has a minimum value atthe central portion of the small arcs on the weakening line contour,

(i) the removable wall. portion comprises in its wall structure anelongated stiffening profile consisting of two parallel ribs protrudingabove the general plane of the closure wall and forming a groove-shapedrecess between them,

(j) the major axis of said stiffening profile coincides with the majordiameter of the weakening line contour and intersects each one of thesmall arcs at midpoint,

(k) the resistance against deflection of the removable wall portionunder an outside force applied to its center region is markedly higherin the axis of said stitfening profile as compared to the remainder ofthe removable wall portion so as to cause this force to be transmittedmainly to the points of intersection on the weakening line,

(I) the aforementioned groove-shaped recess is adapted to receive oneend portion of an independent rigid member for forcible engagementtherewith and which, upon being pivoted, transmits leverage-augmentedbending load to the stiffening profile and to the points of intersectionon the weakening line,

said end closure thus providing considerably difiering resistanceagainst severance at the weakening line, depending on whether it issubjected to uniform internal pressure causing compression stress at theweakening line, or whether it is subjected to an opening force, such asproduced by thumb pressure applied from outside to the center of theremovable wall portion, which force is transmitted mainly to the leastresistant portions of the weakening line, thereby causing tension stressaugmented by the condition of stress concentration and consequentrupture thereat, also providing for an alternate opening method wherebya rigid member is used to produce 1everage-augmented bending forces andconsequent rupture at said least resistant portions of the weakeningline.

10. A sheet metal end closure as set forth in claim 9 where (m) theexterior one of the two parallel ribs is adapted to transmit lateralfoces from the groove-shaped recess to the exterior arc of the weakeningline contour, said end closure thus providing for a still furtheropening method whereby the aforementioned rigid member is pivoted awayfrom the closure center, thereby producing leverage-augmented shearforces and consequent rupture at the exterior arc of the weakening linecontour.

11. A sheet metal end closure as set forth in claim 9 where (n) the wallof the non-removable wall portion comprises a marginal bevel adjacent toand surrounding the weakening line, with the weakening line and theremovable wall portion being relatively recessed toward the inside ofthe closure, said end closure thus providing in addition for aprotective marginal bevel around any sharp edge that might be left afterseverance of the removable wall portion from the non-removable wallportion.

References Cited UNITED STATES PATENTS 982,535 1/ 1911 Rudkiewicz 220271,639,059 8/1927 Saloun 2'15-46 1,851,617 3/ 1932 Buschman 2202-72,119,533 6/1938 Fink 22048 2,120,186 6/1938 Punte 220-27 2,176,89810/1939 Fried 22027 2,289,452 7/1942 Punte 22027 2,312,358 3/1943 Punte22027 2,344,894 3/ 1944 Ottesen 220-28 2,383,274 8/ 1945 Punte 220482,601,937 7/1952 Ottensen 22048 2,630,238 3/ 1953 Battersby 220--273,227,304 1/1966 Asbury 22048 FOREIGN PATENTS 472,481 3/ 1951 Canada.

392,590 5/1933 Great Britain.

55,553 8/193-5 Norway. 80,064 4/ 1934 Sweden.

'DONALD F. NORTON, Primary Examiner.

JAMES R. GARRETT, THERON E. CONDON,

Examiners.

1. A SHEET METAL END CLOSURE FOR A PRESSURE-RESISTANT CONTAINER WITH AWEAKENING LINE DEFINING THE CONTOUR OF A PREDETERMINED REMOVABLE WALLPORTION FROM A NONREMOVABLE WALL PORTION WHERE (A) THE WALL MATERIAL ONONE SIDE OF THE WEAKENING LINE IS DISPLACED SUBSTANTIALLY AT RIGHTANGLES TO THE INITIALLY UNDISPLACED SURFACE WITHOUT BEING SERVED FROMTHE ADJACENT WALL MATERIAL ON THE OPPOSITE SIDE OF THE WEAKENING LINE,(B) THE REMOVABLE WALL PORTION IS RELATIVELY DEPRESSED TOWARD THE INSIDEOF THE END CLOSURE AS A RESULT OF SAID DISPLACEMENT, (C) THE EDGEDEFINED BY THE PERIPHERY OF THE REMOVABLE WALL PORTION UNDERLAPS THECORRESPONDING EDGE OF THE NON-REMOVABLE WALL PORTION, AND THE UPPER FACEOF THE REMOVABLE WALL PORTION IS AT OR ABOVE THE LOWER FACE OF THENON-REMOVABLE WALL PORTION IN THE AREA OF THE WEAKENING LINE, (D) THECROSS-SECTIONAL WALL THICKNESS IN THE AREA OF THE WEAKENING LINEDECREASES ABRUPTLY FROM FULL WALL THICKNESS TO THE NARROWEST RESIDUALCONNECTION BETWEEN THE TWO WALL PORTIONS SO AS TO CAUSE CONDITIONS OFSTRESS CONCENTRATION UNDER TENSIONAL STRESS,